1. Technical Field
The present invention relates to the lithographic printing art, and more particularly refers to a coating plate utilized in coating selected areas of printed material produced by a lithographic printing press.
2. Background Art
In the lithographic printing art the lithographic press applies printing ink on sheets of paper, paperboard, plastic, or other materials to form printed matter in the form of text, logos, or patterns of various sorts. After the printed matter is formed, either after the ink has dried, or even before, it is conventional to apply a coating over selected areas of the printed sheet. This process is generally termed spot or pattern coating. Spot coating constitutes applying a coating in small areas surrounded by a lack of coating in large surrounding areas. Alternatively, a coating, termed "pattern coating", may be applied in large areas, and with the absence of coating in small selected areas. The coating may be applied for various reasons. In some instances the coating may be applied to protect the printed material. In other cases a coating may be applied to the printed material while the ink is still wet or tacky to prevent its sticking to other sheets when placed in a pile of sheets. The coating also provides better scuff resistance. The coating may also be applied to selected areas for aesthetic reasons. For example, it is sometimes desired to provide gloss to certain areas of the sheet in order to provide highlighting, while leaving other areas dull. Additionally, when certain areas of printed folding cartons must be coated with an adhesive, it is desirable or necessary to avoid coating the areas that contain the adhesive. Consequently, pattern coating is used to avoid those areas.
As commonly used in one method of the prior art, the coating process is accomplished by mounting a composite rubber/fabric blanket on a metal coating cylinder. A pattern is then printed onto the surface of the rubber blanket with printing ink, designating the areas to be coated and the areas to remain uncoated. An operator of the press crew then takes a knife or razor blade and cuts away all the areas where there is no ink, all the way down to a layer of fabric in the composite blanket. This process is expensive and takes considerable time. The cost of the rubber mat is considerable. Additionally, while the cutting of the rubber mat is taking place, the press is down. The cutting away of the portions of the rubber mat can take from one half hour to two hours. Press time is generally rated at from $200 to $600 per hour. It is clear that the cost of preparing a coating plate can become a real burden, particularly for small shops generally having a preponderance of short run jobs, where preparation time can be as long as, or longer than, run time.